Aluminum-base alloy



Patented Apr, 9, 11935 UNITED STATES ALUMINUM-BASE ALLOY William E. Mansfield, Garfield Heights, Ohio No Drawing.

- 12 Claims.

15 larger quantities in Furthermore, when the alloys are melted'in iron pots and cast in permanent or semi-permanent molds, the amount of iron dissolved in the aluminum from the melting and casting equip-' ment is often considerable. When iron is pressmall amounts in many alloys utilized for making castings, however, it lowers are consequently interior to castings prepared from similar alloys having the desired minimum iron content, both with respect to finish and to physical properties.

I have made the discovery that ii antimony is added to aluminum base alloys containing iron, an alloy will be produced that has casting properties superior to the present alloys, and this is especially true with respect to alloys which are I seriously aifected by the presence of more than a small amount of iron, such as aluminum-nickel 40 or aluminum-copper alloys. The antimony I serves to break up the large crystalline structure caused by the high iron content, and this is true whether the castings are prepared in sand or chill molds. My discovery, however, is of particular importance in preparing chill mold castings in which secondary aluminum having a compara ,"tively high iron content is utilized because it eliminates porosity, increases the strengthens the casting.

It is, therefore, an object of my invention to provide an aluminum base alloy containing antimony and a substantial amount'of iron.

Another object of my inventlonis to provide an aluminum base alloycontaining iron in substantial amounts and sufficient antimony to diminish ductility and 1 more than 2% of iron,

ApplicatlonDecember 12, 1934, Serial No. 157,216v

(Cl. 75-1) v the deleterious effects of the iron so that an alloy will be produced having good casting. properties, even when the iron is relatively high.

A further object of my invention is to provide an aluminum base alloy containing a substantial amount of antimony that may be cast in sand, permanent molds or dies and from' which good castings may be produced, although a lower grade aluminum having a higher iron content is utilized as the initial material in forming the alloy.

Another object of my invention is to provide an aluminum base alloy containing iron and copper or nickel, or a mixture of copper and nickel, and a substantial amount of antimony.

A further object of myinvention is to provide 1 an alloy containing a substantial amount ol' iron which is particularly adapted to be cast in a permanent mold or from which die castings may I be made.

As previously specified, in preparing aluminum 50 alloys for casting purposes, and particularly castings formed in permanent molds or by the die casting process, it ,has heretofore been found necessary to utilize a good grade aluminum which is comparatively low iniron. In accordance with my invention, however, the iron may be present in the aluminum in amounts ranging from more than 1 to 10% and I am, therefore, able'to producehigh grade castings from lower grade material than that formerly utilized for such purposes. Furthermore, my alloy will not attack the melting or casting equipment in the same degree as many of the alloys now in use. The life 01' this equipment will, therefore, be prolonged, and this is especially true of die casting equipment. I 35 In practicing my invention, antimony is added to a molten bath containing at least 75% aluminum and from more than 1 up to 10% iron, The amount of antimony which is added is somewhat dependent upon the method by which it is '40 introduced. In this connection, it may be stated that it is somewhat diflicult to introduce antimony into the alloy withoutoxidizing a portion of the antimony or preventing a portion of it from segregating from the molten metal. Suflicient antimony is added, however, sothat the cast alloy will contain from .05% to 15%, by weight, 01' antimony. If the aluminum utilized contains say from 3% to 10%, it usually requires more antimony to be present in thefinal alloy than when the iron is below 3%. While I have indicated that 15% of antimony may be p esent in the final casting, betteroastings will be obtained when the amount of antimony is below 7%. preparing castings from secondarytin should be maintained below .5%,

I should be maintained below .5%

, 75 to 150 parts antimony,

aluminum, I prefer to utilize from approximately .1% to 4% of antimony depending upon the amount of iron which is present.

I may also add copper or nickel in amounts ranging from 2% to 15% copper and 2% to 10% nickel. I prefer, however, to maintain the nickel or copper, or a mixture of both, in proportions ranging from 2% to 7%. One or more other elements may also be present, such as chromium,

titanium or cobalt, in effective amounts up to 5%.

The amount of aluminum which is present will, therefore, vary from approximately 75% to 96%, depending upon the amount of alloying ingredients which are present. The amount of aluminum which is present, however, will generally be at least 80%.

When the alloy is to be cast in permanent or semi-permanent molds or by the die casting process, it is also desirable that the alloy should be substantially free from metals, such as zinc, manganese, magnesium, tin and lead. For example, .in preparing an alloy for die casting purposes, the amount of manganese, magnesium, lead and respectively, and the amount of zinc should be below 3% and preferably below 2%. Magnesium in particular has a very pronounced effect upon the hot shortness of aluminum alloys; a property which is very deleterious in producing alloys in permanent or semi-permanent molds or by the die casting process. The magnesium also increases the hardness, which decreases the machinability and causes excessive breakage in trimming. In protherefore essential,

ducing castings in dies, it is that the amount of magnesium which is present and preferably from .05% to .l%. It will of course be understood that in preparing my improved alloys, magnesium is to be considered as an impurity and need not be present many amount. It is very essential, however, that it should not be present in amounts greater than .5%.

Manganese may also be present in amounts ranging up to 3%. Large amounts of manganese,

however, cause the alloy to become brittle.

Silicon may also be present in the aluminum alloy in proportions ranging from effective amounts up to When large amounts of silicon are present, however, the silicon has the tendency to precipitate the antimony out of solution. I, therefore, prefer to maintain the amount of silicon below 3% especially when the iron is high.

When the amount of iron is low, larger amounts of silicon may be present.

' The alloy may be prepared in anydesiredl manner, such as by melting the ingredients together, introducing the antimonyinto molten aluminum, or, if other metals are present, the antimony may be alloyed with such metals and introduced into the molten bath. Another convenient method is to prepare a rich alloy of antimony and aluminum, such as one containing approximately 10% to antimony, and introduce the alloy into the molten aluminum. I may also introduce the antimony in the presence or in the form of a fluoride. For example, I may form a briquette, or an intimate mixture containing approximately 11 parts aluminum powder and 56 parts of sodium silico-fluoride, and introduce it into the aluminum bath.

When a briquette or intimate mixture containing such a composition is introduced into the is in the nascent state acts as a deoxidizing agent and any silica unreduced by the aluminum or any alumina that is formed dissolves in the sodium aluminum fluoride which acts as a flux. By introducing the antimony into the aluminum in such a manner, the bath is deoxidized and the antimony alloys more readily with the aluminum. Instead of utilizing sodium silico-fluoride and causing. a reaction to take pla.ce,. it will of course be understoodthat a mixture of the antimony and other double fluorides, such as sodium aluminum fluoride, may be employed.

My invention is especially suitable for producing aluminum alloys for chill mold or die casting purposes. It is well known that iron has a harmful effect upon the usual die casting alloys, as it causes the alloy to become sluggish in the casting operation and brittle in the finished product. In accordance with the proposed recommendation for composition limits for die casting alloys by the American Society for Testing Materials in 1928, the amount of iron in such alloys is limited to a maximum of 2%. Such limits are considered high by most manufacturers, and in accordance with the best practice, the amount of iron in the metal as charged into the die casting pot is maintained at less than 1.25%. When antimony is added to such alloys, however, good castings may be obtained even when the iron is considerably in excess of 2%. I have found that the antimony increases the elongation and reduces the brittleness of aluininum alloys containing a substantial amount of iron. Antimony also reduces the shrinkage of the alloy during solidification.

. Itv is also well known that excess iron seriously affects the casting properties of aluminum-copper or aluminum nickel alloys containing approximately 2% to 14% copper, or 2% to 10% nickel respectively. When antimony is added to such alloys, however, the injurious. effect of the iron which may be present is diminished, and an alloy may be produced that has good casting properties in permanent or semi-permanent. molds or which may be satisfactorily cast by die-casting proc-' esses. such alloys, a beneficial effect will therefore be produced by the addition of antimony even though the amount of iron that is present is comparatively low. a

The following specific examples are given to illustrate and explain my invention, although it will be understood that I do not desire to limit myself to the particular alloys mentioned.

Analuminum-base alloy containing 6% antimony, 4% iron and the balance aluminum was prepared from which chill castings were made. It was found that the castings had good physical properties and were free from shrinks. The castings had a uniform ture, a tensile strength of 14,000 lbs. per square inch, and an elongation of .7 5% in 2 inches.

Another alloy was produced containing 4% iron and 4% antimony. Castings thickness prepared from the alloy had good characteristics, both withrespect to the finish andphysical properties. When previous attempts have been made to cast thin-sectioned castings of this type containing such a high proportion of iron, the castings had the tendency to crack in the mold.

As iron always exists as an impurity in crystalline grain strucof an inch in An additional alloy was prepared containing ferrotitanium conand the 4% iron,-2% antimony, 1% sisting of iron and 25% titanium,

' cations which may remainder aluminum. A good casting was obtained.

'Ihe castings produced in the preceding examples were machineable, and since they were made from aluminum having a substantial iron content, secondary aluminum may be utilized in preparing the alloys. The alloys were capable of being rolled and forged and had good corrosion resisting properties.

In specifying the percentage, of alloying ingredients in the alloy, it will be understood that the range of percentages given refers to \the finished casting, as well as to the alloy itself. In order to produce good castings, it has heretofore been necessary to maintain the amount of iron in the castings below. a certain percentage, which is the total iron in the original alloy as well as that dissolved in the casting operation;

My improved alloy has a lower thermal expansion than alloys in which antimony is not present, which renders it very desirable for use in pistons. g

From the foregoing specification it will be apparent that I have provided analloy, and cast .ings prepared therefrom that contain a substantial amount of iron. A lower grade of aluminum than it hasheretofore been practical to, utilize may therefore be employed.

It will also be seen that by the addition of antimony to secondary aluminum alloys containing from 2% to 10% of iron, the large crystalline structure caused by the high iron contentwill be broken up and castings having comparatively fine grain structure will be obtained. I am, therefore, able to utilize a lower grade of aluminum in forming castings, and this is especially true in preparing castings in chill molds.or by the die casting process-in which it has heretofore been necessary to maintain the amount of iron in the original alloy below a maximum of 2%, and preferably below a maximum of 1.25%. In former practice when attempts were made to prepare die castings from secondary aluminum alloys the surface layers of the castings had a porous center. The addition of antimony to such alloys, however, eliminates the porous center, increases the ductility materially and strengthens the casting.

While I have referred to the alloy disclosed herein as an alloy which may be cast in chill molds without forming shrinkage cracks; it is to be understood that the alloy may also be cast in sand molds without departing from the spirit of my invention. I

It will furthermore be understood that the present invention is not limited to the specific details set forth in the foregoing examples which should be construed as illustrative and not by way of limitation, and in view of the numerous modifibe eifected therein without departing from the spirit and scope of this invention', it is desired imposed as areindicated in the appended claims.

What I claim is: I d '-i.Analuminumbasealloywhichmaybecast in chill. molds without! e cracks. comprising 75%=to 95% aluminum. at least 2% but not more than 10% iron and antimony in amounts ranging from 45% to 15%, the amount I ofmagnesium in said alloy beingless. than .5%.

2.,An-aluminum base alloy which may be cast in chill molds without forming shrinkage cracks. comprising to'95% alumin at least 2% that only such limitations bep a but not more than 10% iron. and antimony in amounts ranging from 2% to 15%, the amount of magnesium in said alloy being less than .5%. r

3. An aluminum base alloy which may be cast in chili molds without forming shrinkage cracks. comprising 75% to aluminum, at least 2% but not more than 10% iron, and antimony inamounts ranging from 2% to 7%, the amount of magnesium in said alloy being less than .5%.

4. An aluminum base alloy which may be cast in chill molds without forming shrinkage cracks,

comprising from 75% to 95% aluminum, 3% to 10% iron, and 2% to 7% antimony, the amount of magnesium'in said alloy being less 5. An 'aluminumbase alloy which in chill molds without forming comprising 75% to 95% aluminum, at least 2% maybecast but not more than 10% iron, 2% to 15% anti mony, 2%, to 14% copper, and- 2% to 10% nickel, the amount of magnesium in said alloy being less than .5%.

than .5%.

shrinkage cracks.

6. An aluminum base alloy which may be cast 4 in chill molds without forming shrinkage cracks, comprising 75% to 95% aluminum, at least. 2% but not more than 10% .iron, 2% to 15% anticomprising 75% to 95% aluminum, at least'2% but not more than 10% iron, 2% to 15% antimony, and silicon in eil'ective amounts greater than incidental mpurities up to 15%, the amount of magnesium in said alloy being less than .5%.

9. A machinable aluminum base alloy which may be cast in dies or permanent molds without forming shrinkage cracks, comprising a predominant amount of aluminum, not more than 10% of 'iron amounts ranging from .5%

mony being present in and antimony in to 15%, the antisumcient amountsto counteract the deleterious effect of the iron. and

the. amount of magnesium in said alloy beingless than .5%.

'10. An aluminum base alloy having a com paratively fine grain structure, comprising a predominant amountof aluminum, 2% to 10% of of antimony, the amount iron and .05% to 15% of magnesium in said amount of antimony and the amount of zinc being less than 2%. I

11. An aluminum base .alloy having a com paratively fine structure, comprising a predominant amount of aluminum. 2% to 10% or ironand from .l..% to 4% of antimony, the amount of um than .1% and the amount of zinc being less than 2%. -1

12. An aluminum base alloy having'a comparatively fine grain structure, comprising a predominant amount' of aluminum, 2% to 10% of iron and from .1% to 15% antimo the amount of magnesium in said alloy being less than l% and the amount of zinc being less than 3%.

, WILLIAM It.

alloy being less than the at least 2% but but not in excess of .5%'

insaidalloybeingless' 25 mony and 2% to 14% copper, the amount of 

